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Boucneau T, Fernandez B, Besson FL, Menini A, Wiesinger F, Durand E, Caramella C, Darrasse L, Maître X. AZTEK: Adaptive zero TE k-space trajectories. Magn Reson Med 2020; 85:926-935. [PMID: 32936490 DOI: 10.1002/mrm.28483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 12/28/2022]
Abstract
PURPOSE Because of short signal lifetimes and respiratory motion, 3D lung MRI is still challenging today. Zero-TE (ZTE) pulse sequences offer promising solutions as they overcome the issue of short T 2 ∗ . Nevertheless, as they rely on continuous readout gradients, the trajectories they follow in k-space are not adapted to retrospective gating and inferred motion correction. THEORY AND METHODS We propose AZTEK (adaptive ZTE k-space trajectories), a set of 3D radial trajectories featuring three tuning parameters, to adapt the acquisition to any moving organ while keeping seamless transitions between consecutive spokes. Standard ZTE and AZTEK trajectories were compared for static and moving phantom acquisitions as well as for human thoracic imaging performed on 3 volunteers (1 healthy and 2 patients with lung cancer). RESULTS For the static phantom, we observe comparable image qualities with standard and AZTEK trajectories. For the moving phantom, spatially coherent undersampling artifacts observed on gated images with the standard trajectory are alleviated with AZTEK. The same improvement in image quality is obtained in human, so details are more delineated in the lung with the use of the adaptive trajectory. CONCLUSION The AZTEK technique opens the possibility for 3D dynamic ZTE lung imaging with retrospective gating. It enables us to uniformly sample the k-space for any arbitrary respiratory motion gate, while preserving static image quality, improving dynamic image quality and guaranteeing continuous readout gradient transitions between spokes, which makes it appropriate to ZTE.
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Affiliation(s)
- Tanguy Boucneau
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France
| | | | - Florent L Besson
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France.,Université Paris-Saclay, Department of Biophysics and Nuclear Medicine, Hopitaux Universitaires Paris-Saclay, Le Kremlin Bicêtre, France
| | - Anne Menini
- Applications & Workflow, GE Healthcare, Menlo Park, California, USA
| | | | - Emmanuel Durand
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France.,Université Paris-Saclay, Department of Biophysics and Nuclear Medicine, Hopitaux Universitaires Paris-Saclay, Le Kremlin Bicêtre, France
| | | | - Luc Darrasse
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France
| | - Xavier Maître
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France
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Effect of spiral undersampling patterns on FISP MRF parameter maps. Magn Reson Imaging 2019; 62:174-180. [PMID: 30654162 DOI: 10.1016/j.mri.2019.01.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 01/11/2019] [Accepted: 01/12/2019] [Indexed: 12/18/2022]
Abstract
PURPOSE Artifacts arising from undersampling are not always treatable as incoherent noise for the pattern matching process in Magnetic Resonance Fingerprinting (MRF). To estimate the effect of undersampling artifacts on MRF quantitative results, spiral sampling trajectories and their temporal variation is examined. METHODS The effect of sampling trajectories and their variation during the MRF experiment was assessed by characterizing aliasing artifacts. Temporal rearrangements of sampling trajectories were tested and evaluated in simulations and scans of phantoms and in a volunteer brain. RESULTS Results show that some temporal variations of sampling patterns can lead to spatial biases in MRF parameter maps. Observed effects are consistent with derived performance indicators for different interleaving schemes, leading to substantially improved MRF sampling patterns. CONCLUSION With the help of the presented simulation framework, MRF implementations can be investigated and improved. This was demonstrated for a spiral FISP (Fast imaging with steady-state free precession) MRF implementation, where a significantly improved interleaving scheme was identified, and confirmed by experiment.
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Kawaji K, Patel MB, Cantrell CG, Tanaka A, Marino M, Tamura S, Wang H, Wang Y, Carroll TJ, Ota T, Patel AR. A fast, noniterative approach for accelerated high-temporal resolution cine-CMR using dynamically interleaved streak removal in the power-spectral encoded domain with low-pass filtering (DISPEL) and modulo-prime spokes (MoPS). Med Phys 2017; 44:3450-3463. [PMID: 28339110 DOI: 10.1002/mp.12234] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 03/03/2017] [Accepted: 03/03/2017] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To introduce a pair of accelerated non-Cartesian acquisition principles that when combined, exploit the periodicity of k-space acquisition, and thereby enable acquisition of high-temporal cine Cardiac Magnetic Resonance (CMR). METHODS The mathematical formulation of a noniterative, undersampled non-Cartesian cine acquisition and reconstruction is presented. First, a low-pass filtering step that exploits streaking artifact redundancy is provided (i.e., Dynamically Interleaved Streak removal in the Power-spectrum Encoded domain with Low-pass filtering [DISPEL]). Next, an effective radial acquisition for the DISPEL approach that exploits the property of prime numbers is described (i.e., Modulo-Prime Spoke [MoPS]). Both DISPEL and MoPS are examined using numerical simulation of a digital heart phantom to show that high-temporal cine-CMR is feasible without removing physiologic motion vs aperiodic interleaving using Golden Angles. The combined high-temporal cine approach is next examined in 11 healthy subjects for a time-volume curve assessment of left ventricular systolic and diastolic performance vs conventional Cartesian cine-CMR reference. RESULTS The DISPEL method was first shown using simulation under different streak cycles to allow separation of undersampled radial streaking artifacts from physiologic motion with a sufficiently frequent streak-cycle interval. Radial interleaving with MoPS is next shown to allow interleaves with pseudo-Golden-Angle variants, and be more compatible with DISPEL against irrational and nonperiodic rotation angles, including the Golden-Angle-derived rotations. In the in vivo data, the proposed method showed no statistical difference in the systolic performance, while diastolic parameters sensitive to the cine's temporal resolution were statistically significant (P < 0.05 vs Cartesian cine). CONCLUSIONS We demonstrate a high-temporal resolution cine-CMR using DISPEL and MoPS, whose streaking artifact was separated from physiologic motion.
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Affiliation(s)
- Keigo Kawaji
- Department of Medicine, The University of Chicago, Chicago, IL, USA
| | - Mita B Patel
- Department of Medicine, The University of Chicago, Chicago, IL, USA
| | | | - Akiko Tanaka
- Department of Surgery, The University of Chicago, Chicago, IL, USA
| | - Marco Marino
- Department of Medicine, The University of Chicago, Chicago, IL, USA
| | - Satoshi Tamura
- Department of Electrical, Electronic and Computer Engineering, Gifu University, Gifu City, Japan
| | | | - Yi Wang
- Departments of Biomedical Engineering and Radiology, Cornell University, New York, NY, USA
| | - Timothy J Carroll
- Department of Radiology, The University of Chicago, Chicago, IL, USA
| | - Takeyoshi Ota
- Department of Surgery, The University of Chicago, Chicago, IL, USA
| | - Amit R Patel
- Departments of Medicine and Radiology, The University of Chicago, Chicago, IL, USA
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Park J, Shin T, Yoon SH, Goo JM, Park JY. A radial sampling strategy for uniform k-space coverage with retrospective respiratory gating in 3D ultrashort-echo-time lung imaging. NMR IN BIOMEDICINE 2016; 29:576-87. [PMID: 26891126 PMCID: PMC4833643 DOI: 10.1002/nbm.3494] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 12/22/2015] [Accepted: 01/01/2016] [Indexed: 05/07/2023]
Abstract
The purpose of this work was to develop a 3D radial-sampling strategy which maintains uniform k-space sample density after retrospective respiratory gating, and demonstrate its feasibility in free-breathing ultrashort-echo-time lung MRI. A multi-shot, interleaved 3D radial sampling function was designed by segmenting a single-shot trajectory of projection views such that each interleaf samples k-space in an incoherent fashion. An optimal segmentation factor for the interleaved acquisition was derived based on an approximate model of respiratory patterns such that radial interleaves are evenly accepted during the retrospective gating. The optimality of the proposed sampling scheme was tested by numerical simulations and phantom experiments using human respiratory waveforms. Retrospectively, respiratory-gated, free-breathing lung MRI with the proposed sampling strategy was performed in healthy subjects. The simulation yielded the most uniform k-space sample density with the optimal segmentation factor, as evidenced by the smallest standard deviation of the number of neighboring samples as well as minimal side-lobe energy in the point spread function. The optimality of the proposed scheme was also confirmed by minimal image artifacts in phantom images. Human lung images showed that the proposed sampling scheme significantly reduced streak and ring artifacts compared with the conventional retrospective respiratory gating while suppressing motion-related blurring compared with full sampling without respiratory gating. In conclusion, the proposed 3D radial-sampling scheme can effectively suppress the image artifacts due to non-uniform k-space sample density in retrospectively respiratory-gated lung MRI by uniformly distributing gated radial views across the k-space.
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Affiliation(s)
- Jinil Park
- Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, South Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
| | - Taehoon Shin
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, MD, USA
| | - Soon Ho Yoon
- Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea
- Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, South Korea
| | - Jin Mo Goo
- Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea
- Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, South Korea
- Cancer Research Institute, Seoul National University, Seoul, South Korea
| | - Jang-Yeon Park
- Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, South Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
- Correspondence to: J.-Y. Park, Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, South Korea.
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Sharif B, Dharmakumar R, Arsanjani R, Thomson L, Merz CNB, Berman DS, Li D. Non-ECG-gated myocardial perfusion MRI using continuous magnetization-driven radial sampling. Magn Reson Med 2014; 72:1620-8. [PMID: 24443160 PMCID: PMC4102672 DOI: 10.1002/mrm.25074] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 10/31/2013] [Accepted: 11/17/2013] [Indexed: 01/18/2023]
Abstract
PURPOSE Establishing a high-resolution non-ECG-gated first-pass perfusion (FPP) cardiac MRI technique may improve accessibility and diagnostic capability of FPP imaging. We propose a non-ECG-gated FPP imaging technique using continuous magnetization-driven golden-angle radial acquisition. The main purpose of this preliminary study is to evaluate whether, in the simple case of single-slice two-dimensional imaging, adequate myocardial contrast can be obtained for accurate visualization of hypoperfused territories in the setting of myocardial ischemia. METHODS A T1-weighted pulse sequence with continuous golden-angle radial sampling was developed for non-ECG-gated FPP imaging. A sliding-window scheme with no temporal acceleration was used to reconstruct 8 frames/s. Canines were imaged at 3T with and without coronary stenosis using the proposed scheme and a conventional magnetization-prepared ECG-gated FPP method. RESULTS Our studies showed that the proposed non-ECG-gated method is capable of generating high-resolution (1.7 × 1.7 × 6 mm(3) ) artifact-free FPP images of a single slice at high heart rates (92 ± 21 beats/min), while matching the performance of conventional FPP imaging in terms of hypoperfused-to-normal myocardial contrast-to-noise ratio (proposed: 5.18 ± 0.70, conventional: 4.88 ± 0.43). Furthermore, the detected perfusion defect areas were consistent with the conventional FPP images. CONCLUSION Non-ECG-gated FPP imaging using optimized continuous golden-angle radial acquisition achieves desirable image quality (i.e., adequate myocardial contrast, high spatial resolution, and minimal artifacts) in the setting of ischemia.
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Affiliation(s)
- Behzad Sharif
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Rohan Dharmakumar
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Reza Arsanjani
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Louise Thomson
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Barbra Streisand Women’s Heart Center, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - C. Noel Bairey Merz
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Barbra Streisand Women’s Heart Center, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Daniel S. Berman
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Debiao Li
- Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
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Application of basic physics principles to clinical neuroradiology: differentiating artifacts from true pathology on MRI. AJR Am J Roentgenol 2013; 201:369-77. [PMID: 23883218 DOI: 10.2214/ajr.12.10394] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE This article outlines artifactual findings commonly encountered in neuroradiologic MRI studies and offers clues to differentiate them from true pathology on the basis of their physical properties. Basic MR physics concepts are used to shed light on the causes of these artifacts. CONCLUSION MRI is one of the most commonly used techniques in neuroradiology. Unfortunately, MRI is prone to image distortion and artifacts that can be difficult to identify. Using the provided case illustrations, practical clues, and relevant physical applications, radiologists may devise algorithms to troubleshoot these artifacts.
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Abstract
In recent years, there has been an explosive growth of magnetic resonance imaging (MRI) techniques that allow faster scan speed by exploiting temporal or spatiotemporal redundancy of the images. These techniques improve the performance of dynamic imaging significantly across multiple clinical applications, including cardiac functional examinations, perfusion imaging, blood flow assessment, contrast-enhanced angiography, functional MRI, and interventional imaging, among others. The scan acceleration permits higher spatial resolution, increased temporal resolution, shorter scan duration, or a combination of these benefits. Along with the exciting developments is a dizzying proliferation of acronyms and variations of the techniques. The present review attempts to summarize this rapidly growing topic and presents conceptual frameworks to understand these techniques in terms of their underlying mechanics and connections. Techniques from view sharing, keyhole, k-t, to compressed sensing are covered.
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Affiliation(s)
- Jeffrey Tsao
- Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA.
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Lin W, Huang F, Duensing GR, Reykowski A. High temporal resolution retrospective motion correction with radial parallel imaging. Magn Reson Med 2011; 67:1097-105. [PMID: 21842499 DOI: 10.1002/mrm.23092] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 06/08/2011] [Accepted: 06/20/2011] [Indexed: 11/07/2022]
Abstract
A method for motion correction in multicoil imaging applications, involving both data collection and reconstruction, is presented. A bit-reversed radial acquisition scheme, in conjunction with a rapid self-calibrated parallel imaging method, Generalized auto-calibrating partial parallel acquisition (GRAPPA) operator for wider radial bands (GROWL), is used to achieve motion correction at a high temporal resolution. View-by-view in-plane motion correction is achieved in 2D imaging, while 3D motion correction is achieved for every two consecutive slice-encoding planes in 3D imaging. In the proposed technique, GROWL contributes in two aspects: First, a central k-space circle/cylinder used as the motion-free reference is generated from a small number of radial lines/planes; Second, undersampled k-space regions resulting from rotation and inconsistent (e.g. intraview and nonrigid body) motion can be filled in. When compared with navigator-based motion correction methods, the proposed method does not prolong scan time and can be applied to short-TR sequences. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.
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Affiliation(s)
- Wei Lin
- Invivo Corporation, Philips Healthcare, Gainesville, FL, USA.
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9
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Tsao J. Ultrafast imaging: Principles, pitfalls, solutions, and applications. J Magn Reson Imaging 2010; 32:252-66. [DOI: 10.1002/jmri.22239] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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Lee GR, Griswold MA, Tkach JA. Rapid 3D radial multi-echo functional magnetic resonance imaging. Neuroimage 2010; 52:1428-43. [PMID: 20452436 DOI: 10.1016/j.neuroimage.2010.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 04/27/2010] [Accepted: 05/01/2010] [Indexed: 11/29/2022] Open
Abstract
Functional magnetic resonance imaging with readouts at multiple echo times is useful for optimizing sensitivity across a range of tissue T2* values as well as for quantifying T2*. With single-shot acquisitions, both the minimum TE value and the number of TEs which it is possible to collect within a single TR are limited by the long echo-planar imaging readout duration (20-40 ms). In the present work, a multi-shot 3D radial acquisition which allows rapid whole-brain imaging at a range of echo times is proposed. The proposed 3D k-space coverage is implemented via a series of rotations of a single 2D interleaf. Data can be reconstructed at a variety of temporal resolutions from a single dataset, allowing for a flexible tradeoff between temporal resolution and BOLD contrast to noise ratio. It is demonstrated that whole-brain images at 5 echo times (TEs from 10 to 46 ms) can be acquired at a temporal rate as rapid as 400 ms/volume (3.75 mm isotropic resolution). Activation maps for a simultaneous motor/visual task consistent across multiple acceleration factors are obtained. Weighted combination of the echoes results in Z-scores that are significantly (p=0.016) higher than those resulting from any of the individual echo time images.
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Affiliation(s)
- Gregory R Lee
- Department of Radiology, School of Medicine, Case Western Reserve University/University Hospitals Case Medical Center, Cleveland, Ohio 44106, USA
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Lin W, Guo J, Rosen MA, Song HK. Respiratory motion-compensated radial dynamic contrast-enhanced (DCE)-MRI of chest and abdominal lesions. Magn Reson Med 2009; 60:1135-46. [PMID: 18956465 DOI: 10.1002/mrm.21740] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dynamic contrast-enhanced (DCE)-MRI is becoming an increasingly important tool for evaluating tumor vascularity and assessing the effectiveness of emerging antiangiogenic and antivascular agents. In chest and abdominal regions, however, respiratory motion can seriously degrade the achievable image quality in DCE-MRI studies. The purpose of this work is to develop a respiratory motion-compensated DCE-MRI technique that combines the self-gating properties of radial imaging with the reconstruction flexibility afforded by the golden-angle view-order strategy. Following radial data acquisition, the signal at k-space center is first used to determine the respiratory cycle, and consecutive views during the expiratory phase of each respiratory period (34-55 views, depending on the breathing rate) are grouped into individual segments. Residual intrasegment translation of lesion is subsequently compensated for by an autofocusing technique that optimizes image entropy, while intersegment translation (among different respiratory cycles) is corrected using 3D image correlation. The resulting motion-compensated, undersampled dynamic image series is then processed to reduce image streaking and to enhance the signal-to-noise ratio (SNR) prior to perfusion analysis, using either the k-space-weighted image contrast (KWIC) radial filtering technique or principal component analysis (PCA). The proposed data acquisition scheme also allows for high frame-rate arterial input function (AIF) sampling and free-breathing baseline T(1) mapping. The performance of the proposed radial DCE-MRI technique is evaluated in subjects with lung and liver lesions, and results demonstrate that excellent pixelwise perfusion maps can be obtained with the proposed methodology.
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Affiliation(s)
- Wei Lin
- Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania, USA.
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Cashen TA, Jeong H, Shah MK, Bhatt HM, Shin W, Carr JC, Walker MT, Batjer HH, Carroll TJ. 4D radial contrast-enhanced MR angiography with sliding subtraction. Magn Reson Med 2008; 58:962-72. [PMID: 17969099 DOI: 10.1002/mrm.21364] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A method is presented for high spatial and temporal resolution 3D contrast-enhanced magnetic resonance angiography. The overall technique involves a set of interrelated components suited to high-frame-rate angiography, including 3D cylindrical k-space sampling, angular undersampling, asymmetric sampling, sliding window reconstruction, pseudorandom view ordering, and a sliding subtraction mask. Computer simulations and volunteer studies demonstrated the utility of each component of the technique. Angiograms of one hemisphere of the intracranial vasculature were acquired with a pixel size of 1.1 x 1.1 x 2.8 mm and a frame rate of 0.35 sec based on a temporal resolution of 3.5 sec. Such a 3D time-resolved, or "4D," technique has the potential to noninvasively acquire diagnostic quality images of certain anatomic regions with a frame rate fast enough to not only ensure the capture of an uncontaminated arterial phase, but even demonstrate contrast bolus flow dynamics. Clinical applications include noninvasive imaging of arteriovenous shunting, which is demonstrated with a patient study.
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Affiliation(s)
- Ty A Cashen
- Department of Biomedical Engineering, Northwestern University, Chicago, Illinois, USA
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Abstract
A method for reconstruction of time-resolved MRI called highly-constrained backprojection (HYPR) has been developed. To evaluate the HYPR reconstruction in relation to data sparsity and temporal dynamics, computer simulations were performed, investigating signal modulations under different situations that reflect dynamic contrast-enhanced MR angiography (MRA). In vivo studies were also performed with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) for abdominal MRA in a canine model to demonstrate the application of HYPR for three-dimensional (3D) time-resolved MRA. When contrast dynamics vary over space, large vessels (e.g., veins) tend to introduce signal interference to small vessels (e.g., arteries) in HYPR, particularly when the vessels are in close proximity. The enhancement of background tissue signals may also alter the arterial and venous temporal profiles in HYPR. However, the artifacts are manifest as intensity modulation rather than structural interference, and therefore have little impact on structural diagnosis. Increasing the number of projections per time point increases temporal blur while reducing corruption of temporal behavior from adjacent tissues. Uniformly interleaved acquisition order, such as the bit-reversed order, is important to reduce artifacts. With high signal-to-noise ratio (SNR) and limited artifacts, HYPR reconstruction has potential to greatly improve time-resolved MRA in clinical practice.
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Affiliation(s)
- Yuexi Huang
- Department of Medical Biophysics, University of Toronto, Toronto, Canada.
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